下载文件至本地缓存

- (void)download {
    AFHTTPSessionManager *manger = [AFHTTPSessionManager manager];
    NSString *url = @"网络文件地址";
    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:url]];
    
    NSURLSessionDownloadTask *loadTask = [manger downloadTaskWithRequest:request progress:^(NSProgress * _Nonnull downloadProgress) {
        //下载进度监听
        NSLog(@"Progress:----%.2f%",100.0*downloadProgress.completedUnitCount/downloadProgress.totalUnitCount);
    } destination:^NSURL * _Nonnull(NSURL * _Nonnull targetPath, NSURLResponse * _Nonnull response) {
        NSString *fullPath = [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:response.suggestedFilename];
        NSLog(@"fullPath:%@",fullPath);
        NSLog(@"targetPath:%@",targetPath);
        return [NSURL fileURLWithPath:fullPath];
    } completionHandler:^(NSURLResponse * _Nonnull response, NSURL * _Nullable filePath, NSError * _Nullable error) {
        NSLog(@"filePath:%@",filePath);
    }];
    [loadTask resume];
}